Data display devices have a screen area which possesses a side ratio which is usually 4:3. As the picture element resolution corresponds to this ratio, each picture element information displayed on the screen has a corresponding side length or expansion in x-direction and y-direction. Thus, in the corresponding picture information storage, a true-to-picture pattern of the picture information elements is stored. By the thus obtained square form of the picture elements it is rendered possible to electronically manipulate the stored content in the picture information storage such that on the screen rotary movements of figures, for example, can be displayed without distortion.
Information can also be displayed in the form of pictures with picture elements which differ from the above-described standards of data display devices, as for example, by the video text method. For this method, picture elements are used which have a side ratio of 3:2, i.e. a rectangular form. Then the picture information elements, when displayed on the area of these picture elements, do not have the form of a circular dot but of an ellipse. When, according to the video text method, a square area is displayed, the latter does not consist of the same number of picture information elements in x-direction as in y-direction, but of, for example, 30 picture information elements in the x-direction and 20 in the y-direction.
If such a video text picture is displayed on the screen of a usual data display device, picture distortion occurs which results in the representation of a square as a rectangle with a side ratio which corresponds to the circular picture dots or to the display areas of the picture elements, which have a square form due to the other kind of scanning. This distortion has hardly any influence on the readability of alphanumeric characters when displayed. There is, however, a falsification of the information content in the representation of geometrical figures, as the information will appear more depressed in the y-direction than in the x-direction.